Car Doctor Q&A: Blown Shocks and Out of Balance Tires

This week’s Car Doctor question isn’t about a specific make and model, but a case of a rear tire bouncing down the road.

Q: My wife and I were out on the highway the other day and saw something interesting. There was a car that was in front of me that every time it hit a bump the rear tires bounced like a basketball. When I passed the car the driver didn’t seem to even notice what was going on with his car.

Was this a tire problem, shocks of something else and why didn’t the driver notice?

A: The problem is a combination of issues. The biggest problem with this car was faulty shock absorbers. A shock absorber is designed to keep the tires in contact with the road. The secondary function of a shock absorber is to control the movement of the car’s suspension when turning, braking and accelerating. More than likely the car you saw had a combination of out of balance tires and worn out shocks.

At highway speeds as the tire hit a bump or if it was out of balance it would start to bounce and the worn shocks were not able to control the tire’s movement. If you looked at the tires they would most likely be have a scalloped wear pattern from bouncing on the road. Shock absorbers should be checked periodically for wear and hydraulic leaks. as a general rule shock absorbers wear gradually and more than likely the driver just became accustomed to the sloppy ride and handling.

As far as why the driver didn’t notice? The car had to be so poorly serviced at that point, the vibration hardly mattered.